Transgenic expression of CCK2 receptors sensitizes murine pancreatic acinar cells to carcinogen‐induced preneoplastic lesions formation

Abstract

In humans, initial events of pancreatic carcinogenesis remain unknown, and the question of whether this cancer, which has a ductal phenotype, exclusively arises from duct cells has been raised. Previous studies have demonstrated that transgenic expression of the CCK2 receptor in acinar cells of ElasCCK2 mice plays a role in the development of pancreatic neoplasia. The aim of our study was to examine initial steps of carcinogenesis in ElasCCK2 mice, adding a supplementary defect by using a chemical carcinogen, azaserine. Results of posttreatment sequential immunohistochemical examinations and quantifications demonstrate that mice responded to azaserine. Transition of acinar cells into duct-like cells expressing Pdx1 and gastrin, as well as proliferation of acinar cells, were transiently observed in both transgenic and control mice. The carcinogen also induced formation of preneoplastic lesions, adenomas, exhibiting properties of autonomous growth. Importantly, expression of the CCK2 receptor increased the susceptibility of pancreas to azaserine. Indeed, treated ElasCCK2 mice exhibited larger areas of pancreatic acinar-ductal transition, increased cellular proliferation as well as larger adenomas areas vs. control mice. These amplified responses may be related to auto/paracrine stimulation of CCK2 receptor by gastrin expressed in newly formed duct-like cells. Our results demonstrate that activation of CCK2 receptor and azaserine result in cumulative effects to favor the emergence of a risk situation that is a potential site for initiation of carcinogenesis. ' 2005 Wiley-Liss, Inc.Key words: G protein coupled receptors; CCK2 receptor; precancerous conditions; gastrin; transdifferentiation; experimental animal model; developmental gene Peptides of the cholecystokinin (CCK)/gastrin family are present in the gastrointestinal tract where they are known to physiologically regulate gallbladder and bowel motility, pancreatic and gastric secretion as well as growth and trophicity of gastrointestinal epithelial mucosa. 1 Two receptors that mediate the actions of cholecystokinin and gastrin have been pharmacologically classified as CCK1 and CCK2 receptors on the basis of their binding affinity for their natural ligands. While the CCK1 receptor is highly selective towards cholecystokinin vs. gastrin, the CCK2 receptor binds the 2 agonists with similar high affinities. 2 Both are G-protein coupled receptors with extrinsic tyrosine kinase activity. They activate many intracellular mediators classically described in the regulation of mitogenesis by growth factors. 3 Mitogen-activated protein kinases, ERK1/2, Jun kinase and p38MAPK, as well as the phosphatidylinositol 3-kinase (PI3K) and early responsive genes (c-fos, c-myc and c-jun), are known targets of gastrin. 4-7 Several groups including ours, have documented the contribution of Src and focal adhesion kinase (Fak) families' tyrosine kinases upstream the activation of these pathways. 4,8 The role of gastrin and CCK2 receptors as positive regulators of proliferation of normal...

Expression of the Notch Signaling Pathway and Effect on Exocrine Cell Proliferation in Adult Rat Pancreas

“…In contrast, Elas/CCK2 mice which undergo continuous mitogenic stimulation by gastrin do develop tumors in cells that underwent acinoductal conversion. 8 In the caeruleintreated mouse model, a similar transient increase in proliferation was noted as early as after duct ligation but the expression of Notch declined together with a decline in proliferation and together with restoration of the differentiated exocrine state within 1 week. In the duct ligation model it takes more than 14 days to restore normal tissue structure.…”

“…6,7 Gastrin however is also a strong mitogen for the metaplastic cells, 6 and its role in development of pancreatic cancer has been shown. 8 Nevertheless, in the duct ligation model in which this hormone also becomes overexpressed, 9 the cells do not become neoplastic. To complement the in vivo experimental model, we studied an in vitro model of exocrine cell metaplasia.…”

Establishment of an orthotopic pancreatic cancer mouse model: Cells suspended and injected in Matrigel

“…Current animal models of pancreatic cancer include xenograft models [7][8][9] , carcinogen-induced models [10][11][12][13] , and genetically engineered models [14][15][16][17][18] . In the carcinogeninduced model, when pancreatic cancer is induced, hepatocellular carcinoma and other tumors occur simultaneously due to poor specificity of the carcinogen; thereby, the accuracy of using such animal models is limited.…”

Z-360, a Novel Cholecystokinin-2/Gastrin Receptor Antagonist, Inhibits Gemcitabine-Induced Expression of the Vascular Endothelial Growth Factor Gene in Human Pancreatic Cancer Cells

“…9) Moreover, studies on transgenic mice overexpressing the gastrin or CCK-2/gastrin receptors show that gastrin is involved in the development of gastric and pancreatic tumors. 10,11) In the pre-clinical studies of CCK-2/gastrin receptor antagonists, the role of gastrin and the CCK-2/gastrin receptor in human pancreatic carcinogenesis was investigated in vitro by using human pancreatic carcinoma cell lines 12) and in vivo by using xenograft models.…”

“…9) Moreover, studies on transgenic mice overexpressing the gastrin or CCK-2/gastrin receptors show that gastrin is involved in the development of gastric and pancreatic tumors. 10,11) In the pre-clinical studies of CCK-2/gastrin receptor antagonists, the role of gastrin and the CCK-2/gastrin receptor in human pancreatic carcinogenesis was investigated in vitro by using human pancreatic carcinoma cell lines 12) and in vivo by using xenograft models. 6) CCK-2/gastrin receptor antagonists such as L-365260 6,13) inhibited the growth of pancreatic carcinoma-derived cell lines in these models 6,7) ; the results suggesting treatment with a CCK-2/gastrin receptor antagonist is useful for patients with pancreatic cancer expressing this receptor.…”